Temperature dependence of positron-annihilation parameters in YBa2Cu3O7−x above and below the superconducting transition
S. G. Usmar, P. Sferlazzo, K. G. Lynn, A. R. Moodenbaugh
DOI 10.1103/PhysRevB.36.8854 · Physical Review B
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Abstract
The temperature dependence of positron-annihilation parameters for YBa2Cu3O7−x x=0.7, 0.4, and 0.0 are reported. It was found that a transition in the Doppler line-shape parameter S was associated with the superconducting transition temperature (Tc) in YBa2Cu3O7−x x=0.4 and 0.0, while no transition was observed in the nonsuperconducting YBa3Cu3O6.3. Positron lifetime parameters in YBa2Cu3O7 were found to be consistent with positrons localized at open volume regions (probably unoccupied crystallographic sites) in this material with a lifetime of 210 psec. The positron lifetime decreased by approximately 5% across the superconducting transition and subsequently by 4% to 193±1 psec at 12 K. These results indicate that the electron density at this site increases approximately 9% between 100 and 12 K. Doppler line-shape results show that the average electron momentum at the annihilation site increases across the superconducting transition and from sample to sample as the oxygen concentration decreases.
Source-reported materials — not catalogue approval
| Formula | Reported Tc (K) | Pressure (GPa) | Type |
|---|---|---|---|
| YBa2Cu3O7 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 90 | Pressure not reported | midpoint |
| YBa2Cu3O6.6 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 46 | Pressure not reported | midpoint |
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